the face of the moon as it is seen during its revolution around the earth, esp at one of its phases: new moon, full moon

3.

any natural satellite of a planet

4.

moonlight; moonshine

5.

something resembling a moon

6.

a month, esp a lunar one

7.

once in a blue moon, very seldom

8.

(informal) over the moon, extremely happy; ecstatic

9.

reach for the moon, to desire or attempt something unattainable or difficult to obtain

verb

10.

when tr, often foll by away; when intr, often foll by around. to be idle in a listless way, as if in love, or to idle (time) away

11.

(intransitive) (slang) to expose one's buttocks to passers-by

Derived Forms

moonless, adjective

Word Origin

Old English mōna; compare Old Frisian mōna, Old High German māno

Moon1

/muːn/

noun

1.

a system of embossed alphabetical signs for blind readers, the fourteen basic characters of which can, by rotation, mimic most of the letters of the Roman alphabet, thereby making learning easier for those who learned to read before going blind Compare Braille1

Moon2

/muːn/

noun

1.

William. 1818–94, British inventor of the Moon writing system in 1847, who, himself blind, taught blind children in Brighton and printed mainly religious works from stereotyped plates of his own designing

Extended 1665 to satellites of other planets. To shoot the moon "leave without paying rent" is British slang from c.1823; card-playing sense perhaps influenced by gambler's shoot the works (1922) "go for broke" in shooting dice. The moon race and the U.S. space program of the 1960s inspired a number of coinages, including, from those skeptical of the benefits to be gained, moondoggle (cf. boondoggle). The man in the moon is mentioned since early 14c.; he carries a bundle of thorn-twigs and is accompanied by a dog. Some Japanese, however, see a rice-cake-making rabbit in the moon.

v.

c.1600, "to expose to moonlight;" later "idle about" (1836), "move listlessly" (1848), probably on notion of being moonstruck. The meaning "to flash the buttocks" is first recorded 1968, U.S. student slang, from moon (n.) "buttocks" (1756), "probably from the idea of pale circularity" [Ayto]. See moon (n.). Related: Mooned; mooning.

Often Moon. The natural satellite of Earth, visible by reflection of sunlight and traveling around Earth in a slightly elliptical orbit at an average distance of about 381,600 km (237,000 mi). The Moon's average diameter is 3,480 km (2,160 mi), and its mass is about 1/80 that of Earth. See more at giant impact theory.

A natural satellite revolving around a planet.

Our Living Language: The Earth's Moon is a desolate and quiet place. The only natural satellite of Earth, it consists almost entirely of rock, shows no signs of ongoing geologic activity, has no water, and has a very thin atmosphere consisting primarily of sodium. But our Moon does not present a typical case for planetary satellites. Over the last 50 years, over a hundred more moons have been discovered in the solar system, so that they now total 138, nearly all of them orbiting the larger planets Jupiter, Saturn, and Uranus (Mercury, Venus, and Pluto have no moons, while Mars has two). Because they are so far from the Sun, these moons are for the most part extremely cold. Io, one of Jupiter's 63 known moons, is an exception. It is the most geologically active body in the solar system, with almost constant volcanic activity and a surface covered by cooling lava. Some scientists think that another moon of Jupiter, Europa, may have liquid water capable of supporting life underneath a thick layer of surface ice. Titan, one of Saturn's moons, may also be capable of supporting primitive life in the ocean of liquid methane on its frigid surface.

moon definition

A natural satellite of a planet; an object that revolves around a planet. The planets vary in the number of their moons; for example, Mercury and Venus have none, the Earth has one, and Jupiter has seventeen or more. The planets' moons, like the planets themselves, shine by reflected light.

Note: The Earth's moon is about 240,000 miles away and is about 2,000 miles in diameter. The volume of the Earth is fifty times that of the moon; the mass of the Earth is about eighty times that of the moon. The moon has no atmosphere, and its gravity is about one-sixth that of the Earth.